Astronomy & Space

A bizarre track of newborn stars has been discovered to be evidence of a rogue supermassive black hole, according to a new research.

A candidate supermassive black hole has been observed by astronomers hurtling through space for the past 39 million years at a speed of about 4 million miles per hour as it flees from its native galaxy.

a group from Yale University using the Hubble Space Telescope and W. A strange, extremely thin, almost straight streak of young stars and shocked gas was spotted by M. Keck Observatory on Maunakea in Hawaii. This streak is thought to be the path the black hole took as it fled the region.

The results are described in a study that was published in The Astrophysical Journal Letters.

Pieter van Dokkum, professor of astronomy and physics at Yale University and the study’s lead author, declared that “something like this has never been seen anywhere in the universe.”. “Supermassive black holes have been known to exist for a very long time, and it has been predicted for about 50 years that they may occasionally be ejected from galaxies. This would prove this hypothesis since it would be the first proof of a runaway supermassive black hole. “.

F606W F814W HST/ACS image of the linear feature and its surroundings, top left. Image of the F606W zoomed in at top right. The feature has a small bright spot at its pointed, narrow end that appears to get bigger as it moves toward the galaxy. generated from the F606W and F814W images, bottom left: color image LRIS spectra sections close to bright emission lines are shown in the bottom right panel. The galaxy and the feature are both at the same redshift. The feature exhibits intricate variations in the kinematics and line strengths. The Astrophysical Journal Letters (2023). citation: 10.3847/2041-8213/acba86.
Using NASA’s Hubble Space Telescope, Van Dokkum’s team discovered the long feature for the first time. They made additional observations with the Low Resolution Imaging Spectrometer (LRIS) and Near Infrared Echellette Spectrograph (NIRES) at Keck Observatory to get a closer look.

According to Keck Observatory data, the stellar streak was a remarkable 200,000 light-years long and emanated from a compact, star-forming galaxy whose light took 7.6 billion years to reach Earth. The trail’s brightness, which is almost half that of the host galaxy it is connected to, suggests that it is brimming with brand-new stars.

“We believe we see a wake behind the black hole where the gas cools and can form stars.” So we’re looking at star creation in the wake of a black hole. We are witnessing the aftermath. We’re witnessing the wake behind the black hole, much like the wake after a ship.”

Pieter van Dokkum, professor of astronomy and physics at Yale University 

We believe that what we are seeing is a wake left by the black hole, where the gas can cool and give rise to stars. We are therefore examining the star formation that follows the black hole, explained Van Dokkum. “The aftermath is what we’re witnessing. We are observing the black hole’s wake, which is similar to the wake left by a ship.”.

A bright knot of ionized gas, which is likely the location of the black hole itself, was also visible at Keck Observatory at the top of the wake. Additionally, the linear feature’s host galaxy doesn’t appear to have a black hole at its center, or at least not one that is actively devouring matter and emitting potent jets of energy that can be seen by telescopes.

Astronomers have a plausible theory as to how the narrow wake of stars and gas came to be: a black hole that had been ejected from its home galaxy was responsible. First, a merger occurs between two galaxies that both have supermassive black holes at their centers. A third supermassive black hole from another galaxy intrudes on the pair as they are whirling around each other in a binary dance at the center of the newly formed galaxy. The interaction of the three then leads to an unstable situation that generates enough velocity to torpedo one of the three black holes out.

To explain the main characteristics seen, a schematic illustration of the runaway SMBH scenario is provided. The “classic” slingshot scenario is depicted in panels 1–5 (e.g., Saslaw and others, 1974). A long-lived binary SMBH (1, 2) is first created by a merger. A three-body interaction occurs as a result of a third galaxy entering the system (3), the SMBH of which sinks to the center of the newly formed merger remnant, and subsequent events. A large velocity kick is delivered to one black hole, typically the lightest, after it separates from the other two. According to the principle of conservation of linear momentum, the final binary experiences a smaller velocistic kick. All SMBHs have the ability to leave the galaxy if the kicks are big enough (5). Between the events in panels (2) and (3), there could be a gap of about 1 kyr. Approximately 40 myr before the epoch of observation, panels (4 and 5) took place. A frame from the Illustris TNG simulation (Pillepich et al., 2006) serves as the background in figure 6 (2018, with higher gas density in lighter regions. This shows that the circumgalactic medium can have highly asymmetric flows, and we surmise that the SMBH at A is passing through one of these areas of relatively dense and cold CGM (see text). NAOJ is to be credited for the photo in the upper left panel. The Astrophysical Journal Letters (2023). citation: 10.3847/2041-8213/acba86.

Van Dokkum and his team have requested time on NASA’s Chandra X-ray Observatory and James Webb Space Telescope to conduct follow-up observations as a next step in determining whether their discovery is actually a runaway black hole.

Because the linear streak of newborn stars and shocked gas is so striking, van Dokkum claims it should be simple to find other objects similar to it in present and future data, such as with NASA’s upcoming Nancy Grace Roman Space Telescope.

This Hubble Space Telescope historical image captures an odd linear feature that at first was thought to be an imaging artifact from the Hubble’s cameras. However, additional spectroscopic observations show that it is actually a chain of young blue stars that spans 200,000 light-years. At the lower left corner of the bridge, a supermassive black hole can be seen. Right above the galaxy, a black hole was ejected. It left a lengthy trail of brand-new blue stars after compressing gas in its wake. In the history of the universe, nothing like this has ever been observed. The universe was about half its current age when this strange occurrence took place. Image processing: Joseph DePasquale (STScI); credits: NASA, ESA, and Pieter van Dokkum (Yale).
“A lot of what we do consists of testing hypotheses or improving upon previous measurements, but every now and then, a completely unexpected discovery happens. The best! That is rare!” van Dokkum exclaimed.

Imad Pasha, a Yale University graduate student on van Dokkum’s research team who is also an author, said, “Going from noticing the streak and thinking Hey, that’s weird, to this paper was so incredibly fun and satisfying as we were all learning every step of the way.”.

More information: Pieter van Dokkum et al, A Candidate Runaway Supermassive Black Hole Identified by Shocks and Star Formation in its Wake, The Astrophysical Journal Letters (2023). DOI: 10.3847/2041-8213/acba86

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